1. Field of the Invention
The invention relates to high pressure fluid jet nozzle apparatus and in particular to a high pressure fluid jet nozzle having a means for entraining abrasive granules within a high pressure fluid jet and a means and method for preventing wetting and caking of the abrasive granules within the nozzle in the vicinity of the high pressure fluid jet.
2. Description of the prior art
It has been known that a fluid jet, generated by pressurizing a fluid, such as water, and directing such pressurized fluid through a suitable orifice, can cut a wide variety of materials. Such waterjets are currently in use commercially. It has been known also that the capability of such water jets in cutting hard materials can be greatly enhanced by introducing solid particulates, such as abrasives, into the jet stream to generate the so-called abrasive waterjet. In these abrasive waterjet processes, a key system component is the nozzle in which selected abrasives are introduced into the water stream. Many suitable abrasives for these processes are in the form of fine powder or dry granules that can cake up when wetted by fluid, thus blocking the flow. It would be desirable to have a high pressure fluid jet nozzle for entraining abrasive granules within a high pressure fluid jet such that the abrasive granules are kept dry within the nozzle in the vicinity of the high pressure fluid jet and thereby eliminate caking up and clogging of the nozzle at this location. This invention discloses a nozzle design that has an integrated check valve to prevent the wetting of dry abrasives prior to being mixed with the fluid stream. By virtue of this invention, the blockage of abrasive flow frequently encountered in abrasive waterjet processes can be avoided.
Another common problem experienced by nozzles of the prior art which admix abrasive granules with a high pressure fluid stream is erosive wear of the nozzle where the abrasive entrained high pressure fluid stream exits the nozzle. It would be desirable to have a high pressure fluid jet nozzle suitable for mixing abrasive granules with a high pressure fluid jet which will entrain the abrasive granules within the water jet to prevent extensive wear of the nozzle. It would also be desirable to have a high pressure fluid jet nozzle which will provide a predetermined pattern (including both converging and diverging) or multiple high pressure fluid streams to provide for cutting a corresponding kerf pattern.